New digital radio apparatus (digital mobile phones, for example) intended for operation in public data transmission networks are tested for type approval prior to being introduced into the market. The equipment and methods used the testing are usually defmed in data transmission network standards. FIG. 1 illustrates a known test arrangement in which testing is directed to a mobile station (MS) 101 of a cellular radio system. The mobile station may also be called user equipment (UE). A simulation system (SS) 102 simulates a cellular radio system during the test. In this application such a system is called a simulation system or testing system. Testing the functioning of data transmission requires that an active data link 103 be set up between the SS and MS, which may be a radio link or a wire link through a testing interface at the mobile station.
Tests usually apply a technique in which a mobile station receives a downlink frame from the SS and sends back to the SS a corresponding uplink frame which contains the equivalent number of bits. The mobile station may even recycle to the SS the same individual bits that it received in the downlink direction. The SS examines whether the transmission or the operation of the mobile station caused errors in the frame. Arrow 104 depicts the loopback. The arrangement has been suitable for testing the mobile stations of known cellular radio systems since in the known systems the data transmission links are bidirectional and their capacity is distributed symmetrically: the capacities of uplink and downlink data transmission are equal. In mobile stations of new cellular radio systems, however, it is necessary to test functions that involve asymmetric distribution of data transmission capacity between uplink and downlink transmission. Moreover, mobile stations of new cellular radio systems may include functions based on unidirectional downlink data transmission the testing of which is naturally impossible using the method according to the prior art.
From an earlier Finnish patent application no. 981267 by the applicant, which application has not become public by the priority date of this present application, it is known an alternative testing procedure suitable for the testing of data transmission arrangements with asymmetric capacities. In said procedure a mobile station selects from the bits of the downlink frame only a portion which is looped back to the uplink frames. The disadvantage of such an arrangement is that errors in those bits of the downlink frame that are not looped back uplink will remain undetected. In addition, this arrangement, too, is unsuitable for testing unidirectional downlink data transmission links.
From an earlier Finnish patent application no. 990690 by the applicant, which application has not become public by the priority date of this present application, it is known a testing procedure in which the mobile station tested does not need to recycle the transmitted data back uplink. This procedure is based on the fact that the mobile station can produce the same pseudorandom test sequence that the SS includes in the test frames sent downlink. The mobile station compares the test sequence received to the sequence it has produced, produces statistics of the errors detected in the sequence received, and sends uplink to the SS the quantity or errors detected and/or a parameter representing the quantity of errors. A disadvantage of this testing procedure is that it depends on the operation of the algorithm used by the mobile station to produce the reference sequence and detect errors.